1. Field of the Invention
This invention relates to a method for synthesizing crystalline zeolites requiring a reaction mixture for crystallization thereof which contains magadiite as a source of silicon oxide.
2. Description of the Prior Art
Natural and synthetic zeolitic materials of the molecular sieve type are known and are staple items of commerce. Crystalline zeolites are extremely well known in the art and have been the subject of much attention in both the patent and technical literature. These materials have been demonstrated to have catalytic properties for various types of hydrocarbon conversions.
Because of their unique molecular sieving characteristics, as well as their potentially acidic nature, zeolites are especially useful in hydrocarbon processing as absorbents, and, as catalysts, for cracking, reforming, and other hydrocarbon conversion reactions. Although many different crystalline aluminosilicates have been prepared and tested, the search continues for new zeolites which can be used in hydrocarbon and chemical processing.
Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. A number of these zeolites require the presence of a source of organic nitrogen-containing cations in the reaction mixture used to prepare them. Those zeolites include, for example, zeolite ZSM-5 (U.S. Pat. Nos. 3,702,886 and RE 29,948), zeolite ZSM-11 (U.S. Pat. No. 3,709,979), zeolite ZSM-12 (U.S. Pat. No. 3,832,449), zeolite ZSM-23 (U.S. Pat. No. 4,076,842), zeolite ZSM-35 (U.S. Pat. No. 4,016,245), zeolite ZSM-38 (U.S. Pat. No. 4,046,859), zeolite ZK-4 (U.S. Pat. No. 3,314,752), zeolite ZK-22 (U.S. Pat. No. 3,791,964), zeolite "alpha" (U.S. Pat. No. 3,375,205), zeolite "beta" (U.S. Pat. No. 3,308,069), a synthetic erionite (U.S. Pat. No. 3,699,139) and a synthetic offretite (U.S. Pat. No. 3,578,398). A method for synthesizing ZSM-5, ZSM-12, ZSM-35 AND ZSM-38 is disclosed in U.S. Pat. No. 4,151,189.
As is set forth in the above-identified U.S. patents which are incorporated totally herein by reference, these types of zeolites are prepared from a forming solution containing water, a source of organic nitrogen-containing cations, an alkali metal, a source of silica, and a source of alumina. As is known in the art, the forming solution is held at elevated temperatures and pressures until the crystals are formed and thereafter the zeolite crystals are removed.
Prior art sources of silica in preparing zeolites include sodium silicate, colloidal silica, silica hydrosol, silica gel and silicic acid.
A considerable amount of effort has been made to find cheaper routes to zeolites, to find ways to prepare purer forms of the zeolites, and to find ways to prepare zeolites having larger crystal sizes and more ordered crystal structures.
It has now been found that magadiite in its alkali metal form or in the hydrogen form, especially when made synthetically, is a particularly attractive source of silica as it enables useful zeolites to be prepared cheaply, easily and in a purer, larger and more ordered form.